Some Phenomenological Study Of New Physics

The standard model of particle physics is very successful, but as an effective theo-ry, it can not gives explanation or solvation of dark matter, dark energy, the unification of the strong and electroweak interactions, etc, and thus people try to search the trace of new physics. The thing discussed in this article includes the recent result of CDMS II dark matter experiment, the superhadron production at the collider ILC, and the new physics search in the leptonic decays of D0meson.For the underground dark matter experiment, dark matter is searched through ob-serving the signals caused by the scattering between dark matter and the target nucleus. Three signals which may be caused by dark matter were observed by the CDMS â…¡ collaboration in April2013, which favors low mass WIMPs. Taking the CDMS â…¡ new results as input, we first consider a SM singlet dark matter candidate, which interacts with standard model particles through Higgs exchange. It is found that this simplest scenario can not tolerate the CDMS â…¡ data and the stringent constraint set by the L-HC data at the same time, and thus this type dark matter is excluded. Then we make a complete analysis to testify the validity of the scalar, vectorial and fermionic dark matter model with neutral bosons Z0and Z’exchange. It is found that considering the present constraints, e.g., the cross section of the elastic scattering between dark matter and nucleon, the invisible decay width of Z0, and the dark matter relic density in our universe, only if Z’is lighter than Z0, there is still parameter space which is allowed, and one can reconcile all the presently available data.The supersymmetry may be one of the most favorable extensions of the standard model (SM). However, so far at LHC no evidence of the SUSY particles were observed. Of course, there is one more possibility that the SUSY particles have indeed been pro-duced, but are not identified, namely buried in the messy background at hadron collid-ers. If the superpartner of top quark, the t1, is the next-to-lightest SUSY particle and the mass difference between t1and neutrilino is very small, the lifetime of t1would be long enough and hadronize, and the production signals are very difficult to be observed in the large amount of data at hadron collider. In this work, we relate the parameter of t1with the parameter of B meson production in terms of the superflavor symmetry. The cross section of SUSY baryon production is calculated at the future electron-positron collider ILC, and the decay mode is also discussed after the production. For the small mass difference, if the t1-based SUSY hadrons exist, they could be observed at ILC. The mixing and rare decay of neutral meson is a good area in searching for new physics beyond the standard model. In contrast with the down-type B0-B0, Bs-Bs mixing, the SM contribution is more suppressed in up-type D0-D0mixing, a measured relatively large D0-D0mixing in experiment definitely implies the existence of new physics. Meanwhile, it is natural to consider that the rare decays of D meson might be more sensitive to new physics. The new physics contributions of unparticle or an extra gauge boson Z’are discussed in D0â†'μ+μ-, e+e-,μ±e(?) while imposing the constraints set by fitting the D0-D0mixing data, and corresponding branching ratios are calculated. We find that though the new physics gives large contributions in D0-D0mixing, for D0â†'ll, the long-distance SM effects still exceed those contributions of the new physics under consideration. But for a double-flavor changing process such as D0â†'μ±e(?), the new physics contribution would be significant.The trace of the new physics is discussed at BES and/or super charm-tau factory.